This application claims priority under 35 U.S.C. xc2xa7xc2xa7 119 and/or 365 to patent application Ser. No. 0000427-5 filed in Sweden on Feb. 11, 2000; the entire content of which is hereby incorporated by reference.
This invention relates to a tool intended for chip removing machining. In particular, the tool is of the type that comprises a rotatable head having an envelope surface extending rotationally symmetrically around a central axis of geometrical rotation and an end surface extending transversely to said axis, as well as a plurality of tangentially spaced-apart cutting inserts in connection with chip spaces formed in a circumferencial edge portion in the transition between the envelope surface and the end surface. The head includes, on the one hand, an internal, central main duct which has the purpose of conducting a cooling and/or lubricating fluid received from an outside source, and, on the other hand, a number of branch ducts corresponding to the number of cutting inserts and chip spaces with the purpose of individually directing said fluid from the main duct towards the different cutting inserts.
Tools of the type generally described above may be in the form of milling cutters, in particular face mills. Development in modern milling technology is directed towards higher and higher cutting speeds. This development is especially marked in the milling of easily workable materials, such as aluminium. Thus cutting speeds of up to the range of about 8,000-10,000 m/min are already used today in the machining of aluminum. Such speeds for a face mill having a diameter of 100 mm would require rotational speeds in the range of 25,000-32,000 rpm. For different reasons, some sort of fluid is supplied to the individual cutting inserts during the machining operation. In some cases, cooling liquid is supplied for the purpose of cooling the cutting inserts as well as the workpiece and in other cases air with a mist of oil may be supplied for the purpose of providing lubrication and a certain cooling. Also cooling gases may be supplied. Fundamental for the cooling or lubrication fluid is the purpose of giving the machined surfaces on the workpiece optimal properties, to cool the cutting inserts and the workpiece, as well as to counteract smearing of the machined material, e.g. aluminium, on the tool. Another purpose of the fluid is to remove the chips that the cutting inserts remove from the workpiece.
Rotatable tools of the type initially mentioned in general terms are previously known from, e.g., U.S. Pat. No. 960,526 and German Documents DE-3 104 752, DE-4019 506, DE-19 837 704 and DE-3 105 933. Common for these known tools is that the branch ducts from the main duct for the fluid consist of drilled holes.
A rotatable tool holder is previously known from U.S. Pat. No. 5,941,664, which, per se, includes a number of individual fluid branch ducts. The branch ducts are defined by blades, which together form an impeller so as to feed cooling liquid from outside into a central main duct.
German Document DE-197 25 100 describes a milling tool which in connection with the cutting insert-equipped end surface thereof has a central distributor body having a plurality of radially directed nozzles through which cooling liquid may be supplied out to the peripherally situated cutting inserts. However, not even here are any open grooves to be found in said end surface.
Commercially available milling tools, which were known previously, utilise different solutions to lead the cooling and/or lubricating fluid to different cutting inserts on the tool. A commonly occurring solution is based on using branch ducts in the form of holes, which are drilled from points in the immediate vicinity of the individual cutting inserts to a central main duct inside the cutter head. This manufacturing method is, however, complicated and expensive as well as giving mediocre results with regarding the ability of the fluid to cool the cutting inserts and the workpiece and to remove the liberated chips.
The present invention aims at obviating the shortcomings of previously known milling tools and at providing an improved milling tool. Therefore, a primary aim of the invention is to provide a tool which is able to lead the requisite fluid to the different cutting inserts in an effective and powerful manner so as to, in this way, optimise the cooling and/or lubricating effect of the fluid. Furthermore, the invention aims at providing a tool which may guide and make effective the flow of chips from the cutter head in such a way that erosion of the surfaces of the chip spaces is counteracted. Another aim of the invention is to create a tool, which may be manufactured in a simple and inexpensive way. Another aim of the invention is to create a tool having minimum weight, which facilitates operations at high rotational, speeds, in particular in respect to the starting and stopping of the tool.
The present invention involves a tool for chip removing machining which comprises a rotary head that defines a longitudinal axis of rotation. The head includes an envelope surface arranged generally symmetrically relative to the axis, and a front end surface extending transversely relative to the axis. A plurality of circumferentially spaced insert seats are provided in the head for receiving respective cutting inserts. Each insert seat is disposed in a transition region between the envelope surface and the end surface. A main duct extends longitudinally within the head for conducting fluid. The main duct intersects the end surface. A plurality of branch ducts extend transversely from the main duct for conducting fluid from the main duct to the insert seats. Each branch duct is defined by a groove formed in the end surface and is configured to induce a flow of fluid from a fluid inlet end thereof to a fluid outlet end thereof in response to rotation of the head.
Preferably, a substantial portion of each groove is open in the axial direction.